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• What are the differences between programming languages? [closed]

  - by Omega

  Once upon a time, I heard from someone the only difference between programming languages is the syntax I wanted to deny it - to say that there are other fundamental aspects that truly set a language apart from others than just syntax. But I couldn't... So, can you? Whenever I search Google for something like "differences between programming languages", the results tend to be debates between two specific languages (I'd like something more general) - however, some of the aspects that people seemed to debate the most were: Object-Oriented Method/Operator overloading (I actually see this rather related to syntax) Garbage-Collection (While it seems like a good difference, for some reason it doesn't seem that "fundamental") What important aspects other than syntax can you think of?

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• =~ (equal-sign tilde) and m" ... " in .htaccess directive

  - by Lèse majesté

  I saw this bit of code on an old forum post: SSLRequire %{HTTP_HOST} =~ m"\.secure\.powweb\.com" And I was just wondering what the =~ and m" ... " meant. I've been searching online and in the Apache documentation for any mention of the equal-sign tilde operator, but I've found no mention of it. I know that some directives can take a tilde to use a regular expression, but I've never seen the m" ... " form used before. What exactly is that m" ... " for? Where else would you see this form?

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• Do I need the 'w' component in my Vector class?

  - by bobobobo

  Assume you're writing matrix code that handles rotation, translation etc for 3d space. Now the transformation matrices have to be 4x4 to fit the translation component in. However, you don't actually need to store a w component in the vector do you? Even in perspective division, you can simply compute and store w outside of the vector, and perspective divide before returning from the method. For example: // post multiply vec2=matrix*vector Vector operator*( const Matrix & a, const Vector& v ) { Vector r ; // do matrix mult r.x = a._11*v.x + a._12*v.y ... real w = a._41*v.x + a._42*v.y ... // perspective divide r /= w ; return r ; } Is there a point in storing w in the Vector class?

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• Creating a new variable versus assigning an existing one

  - by rwallace

  Which is more common, creating a new variable versus assigning an existing variable (field, array element etc - anything that syntactically uses the assignment operator)? The reason I ask is that I'm designing a new language, and wondering which of these two operations should get the shorter syntax. It's not intended to be a pure functional language, or the question wouldn't arise, so I'd ideally like to count usage across large existing code bases in procedural and object-oriented languages like C, C++ and Java, though as far as I can see there isn't an easy way to do this automatically, and going by memory and eyeball, neither is obviously more common than the other.

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• The rule of 5 - to use it or not?

  - by VJovic

  The rule of 3 (the rule of 5 in the new c++ standard) states : If you need to explicitly declare either the destructor, copy constructor or copy assignment operator yourself, you probably need to explicitly declare all three of them. But, on the other hand, the Martin's "Clean Code" advises to remove all empty constructors and destructors (page 293, G12:Clutter) : Of what use is a default constructor with no implementation? All it serves to do is clutter up the code with meaningless artifacts. So, how to handle these two opposite opinions? Should empty constructors/destructors really be implemented?

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• How to correctly set permisions for all subfolders and files

  - by Saeid87

  I am following the guide to install TinyOS on Ubuntu 12.04 I have done up to step 3, But I am not sure if I have done the step 3 correctly. Because by doing the step 4 I get the permission error : saeid@saeid-Satellite-C660:~$ tos-install-jni /usr/bin/tos-install-jni: 13: [: =: unexpected operator Installing 32-bit Java JNI code in /usr/lib/jvm/java-6-openjdk-i386/jre/lib/i386 ... install: cannot create regular file `/usr/lib/jvm/java-6-openjdk-i386/jre/lib/i386/libgetenv.so': Permission denied Can you please tell me what would be the actual commands for step 3? What I have to replace with following lines?: /opt/tinyos-2.x files: chown -R /opt/tinyos-2.x Change the permissions on any serial (/dev/ttyS), usb (/dev/tts/usb, /dev/ttyUSB), or parallel (/dev/parport) devices you are going to use: chmod 666 /dev/ I mean how would you do those steps in your ubuntu?

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• T-SQL Tuesday: What kind of Bookmark are you using?

  - by Kalen Delaney

  I’m glad there is no minimum length requirement for T-SQL Tuesday blog posts , because this one will be short. I was in the classroom for almost 11 hours today, and I need to be back tomorrow morning at 7:30. Way long ago, back in SQL 2000 (or was it earlier?) when a query indicated that SQL Server was going to use a nonclustered index to get row pointers, and then look up those rows in the underlying table, the plan just had a very linear look to it. The operator that indicated going from the nonclustered...(read more)

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• Most appropriate diagram for GUI button design?

  - by JustADude

  What is the most appropriate diagram for GUI button design? Specifically, I have numerous buttons that will be changing color based on state information from operator input and input from various subcomponents and sensors. I would like to use UML or some other type of design diagrams to be able to capture the color transition. Some folks have suggested sequence diagrams, but I haven't been able to find any good examples that show how to incorporate this design artifact. I would really like to head in this direction to help developers. Thanks a ton for feedback and insights.

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• DOMDocument programming: a lot of little dilemmas, how to solve them?

  - by Peter Krauss

  I need elegance and performance: how to decide by the "best implementation" for each DOM algorithm that I face. This simple "DOMNodeList grouper" illustrate many little dilemmas: use iterator_to_array or "populate an array", when not all items need to be copied. use clone operator, cloneNode method or import method? use parentNode::method() or documentElement::method? (see here) first removeChild or first replaceChild, no avoids "side effects"? ... My position, today, is only "do an arbitrary choice and follow it in all implementations" (like a "Convention over configuration" principle)... But, there are another considerations? About performance, there are some article showing benchmarks? PS: this is a generic DOM question, any language (PHP, Javascript, Python, etc.) have the problem.

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• Are sequence designs appropriate for GUI button design?

  - by JustADude

  Specifically, I have numerous buttons that will be changing color based on state information from operator input and input from various subcomponents and sensors. I would like to use UML or some other type of design diagrams to be able to capture the color transition. Some folks have suggested sequence diagrams, but I haven't been able to find any good examples that show how to incorporate this design artifact. I would really like to head in this direction to help developers. Are sequence designs in fact, appropriate, or is there a more appropriate design?

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• Fixing Gatekeeper Row Cardinality Estimate Issues

  The Query Optimiser needs a good estimate of the number of rows likely to be returned by each physical operator in order to select the best query plan from the most likely alternatives. Sometimes these estimates can go so wildly wrong as to result in a very slow query. Joe Sack shows how it can happen with SQL Queries on a data warehouse with a star schema. Make working with SQL a breezeSQL Prompt 5.3 is the effortless way to write, edit, and explore SQL. It's packed with features such as code completion, script summaries, and SQL reformatting, that make working with SQL a breeze. Try it now.

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• Limitation of high level languages? [closed]

  - by user1705796

  My question may look bit philosophical and nonsense! But I need to know kind of instructions those are not well suitable in high level languages even in c? Or rarely use in the development of software? Like read/write content of CPU registers may useful in debugging programs. And access to cache memory required when developing OS (maybe I am wrong at this point). Is this kind of instruction available languages like Java, Python, C? I also have a second question: And Why all high level languages not having same uniform syntax; at-least same standard library interface name? In python there is and. Or operator is almost same as && and ||. I think Python is developed after C but space indentation is compulsory in Python. Why Python does not use brackets {}. I already know this question going to be highly down-voted.

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• cpan won't configure correctly on centos6, can't connect to internet

  - by dan

  I have Centos 6 setup and have installed perl-CPAN. When I run cpan it takes me through the setup and ends by telling me it can't connect to the internet and to enter a mirror. I enter a mirror, but it still can't install the package. What am I doing wrong? If you're accessing the net via proxies, you can specify them in the CPAN configuration or via environment variables. The variable in the $CPAN::Config takes precedence. <ftp_proxy> Your ftp_proxy? [] <http_proxy> Your http_proxy? [] <no_proxy> Your no_proxy? [] CPAN needs access to at least one CPAN mirror. As you did not allow me to connect to the internet you need to supply a valid CPAN URL now. Please enter the URL of your CPAN mirror CPAN needs access to at least one CPAN mirror. As you did not allow me to connect to the internet you need to supply a valid CPAN URL now. Please enter the URL of your CPAN mirror mirror.cc.columbia.edu::cpan Configuration does not allow connecting to the internet. Current set of CPAN URLs: mirror.cc.columbia.edu::cpan Enter another URL or RETURN to quit: [] New urllist mirror.cc.columbia.edu::cpan Please remember to call 'o conf commit' to make the config permanent! cpan shell -- CPAN exploration and modules installation (v1.9402) Enter 'h' for help. cpan[1]> install File::Stat CPAN: Storable loaded ok (v2.20) LWP not available Warning: no success downloading '/root/.cpan/sources/authors/01mailrc.txt.gz.tmp918'. Giving up on it. at /usr/share/perl5/CPAN/Index.pm line 225 ^CCaught SIGINT, trying to continue Warning: Cannot install File::Stat, don't know what it is. Try the command i /File::Stat/ to find objects with matching identifiers. cpan[2]>

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• Apache: https to https redirect

  - by Klaas van Schelven

  I'm trying to get Apache to redirect all http and https traffic to a single endpoint www.example.org. The http part is easy: <VirtualHost *:80> ServerName example.org Redirect permanent / https://www.example.org/ </VirtualHost> # long list of other domains, all redirecting to https://www.example.org/ <VirtualHost *:80> ServerName www.example.org Redirect permanent / https://www.example.org/ </VirtualHost> I'm trying to do something similar for the https. It is my understanding that I need to specify one specific IP address, because the Host directive is also sent encrypted. So the below works: <VirtualHost xx.xx.xx.xx:443> ServerName www.example.org # actual stuff happening here </VirtualHost> However, when I start adding the redirects to the config, like so: <VirtualHost xx.x.xx.xx:443> ServerName example.org Redirect permanent / https://www.example.org/ </VirtualHost> # long list of other domains stuff breaks. $ apache2ctl configtest [warn] VirtualHost xx.xx.xx.xx:443 overlaps with VirtualHost xx.xx.xx.xx:443, the first has precedence, perhaps you need a NameVirtualHost directive If I add a directive like so: NameVirtualHost xx.xx.xx.xx:443 Connecting to the (ssl part of the) server starts to fail. How do I solve this?

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• How to set up QoS on ADSL router (terracom) for prioritizing browsing

  - by DBZ_A

  I want to configure the ADSL router which connects 10+ machines to the internet. I want to give maximum priority to browsing (ports 80,443) and set low priority for bittorrent etc.(port 42180) I have been experimenting with settings , but with no luck. There are three settings which confuse me, along with my understanding. 802.1 Priority - Related to LAN level, possible values 0-7 , higher numbers means higher priority. 'Mark traffic priority' - clueless about this. IPP/DS - IP Precedence - possible values 0-7 ; 6 & 7 are reserved, so set 5 for highest priority. Or when using DSCP - set 46 for highest priority. Please help me in getting this done... Similer question for another model of router here , but with less number of confusing options :) How to configure QoS on home router Update: from discussion on another thread, QoS can control only upstream traffic (from router to the internet) , while this may in turn affect downstream traffic rate, there is no direct control over data coming into the router.

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• Setting up Apache with multiple virtual host when using Plone 4.1

  - by Shaun Owens

  I have a Plone server running on CentOS, I have multiple instances of Plone running 4.0 and 4.1, I also have multiple sites. I am new to linux and haveing problems getting Apache to work with multiple virtuale hosts. The first host listed works just fine but the second host does not. I get the following error message when I start HTTPD: Starting httpd: [Mon Nov 07 14:38:31 2011] [warn] VirtualHost ordevel3.ucdavis.edu:80 overlaps with VirtualHost ordevel4.ucdavis.edu:80, the first has precedence, perhaps you need a NameVirtualHost directive. What am I missing to get the virtual hosts to work correctly? Below in my syntax in httpd.conf. <VirtualHost ordevel3.abc.edu:80> ServerAlias ordevel3.abc.edu ServerAdmin [email protected] ServerSignature On <IfModule mod_rewrite.c> RewriteEngine On # serving icons from apache 2 server RewriteRule ^/icons/ - [L] RewriteRule ^/(.*) \ http://localhost:8080/VirtualHostBase/http/%{SERVER_NAME}:80/itsdevel3/VirtualHostRoot/$1 [L,P] </IfModule> <IfModule mod_proxy.c> ProxyVia On # prevent the webserver from beeing used as proxy <LocationMatch "^[^/]"> Deny from all </LocationMatch> </IfModule> </VirtualHost> <VirtualHost ordevel4.abc.edu:80> ServerAlias ordevel4.abc.edu ServerAdmin [email protected] ServerSignature On <IfModule mod_rewrite.c> RewriteEngine On # serving icons from apache 2 server RewriteRule ^/icons/ - [L] RewriteRule ^/(.*) \ http://localhost:8180/VirtualHostBase/http/%{SERVER_NAME}:80/ITS/VirtualHostRoot/$1 [L,P] </IfModule> <IfModule mod_proxy.c> ProxyVia On # prevent the webserver from beeing used as proxy <LocationMatch "^[^/]"> Deny from all </LocationMatch> </IfModule> </VirtualHost>

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• What options to use for Accurate bacula backup?

  - by Kiss Stefan

  It's actually 2 question in one. First is a bit more theoretically. So when specifying accurate options how does bacula figure out if a file needs to be backed up ? it's a simple AND ? As in if the options are Accurate = sm5 bacula will not backup the file if ((size = old size) AND (modtime = old modtime) AND (md5 = old md5)) Is that correct ? Do any of the options take precedence ? as in would be a file skipped if modif time is diffreent but it has the same md5sum ? Are there any implied options that you cannot ignore ? Practical case, ( bacula 5.0.1 ) I have to back-up a svn repo, in order to be able to make incremental backups as simple as posible i am hotcopying (client run before) it to another location, that bacula will backup ( then delete it with client run after). Now in the fileset i have Accurate = spnd5 This should tell bacula to take into consideration size , permission bits number of links , decreases in size and md5sum. However , an incremental is also including a full copy of the svn. What am i doing wrong ? it seems that it takes into account creation time even tho i have not specified it.

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• What options to use for Accurate bacula backup ?

  - by Kiss Stefan

  It's actually 2 question in one. First is a bit more theoretically. So when specifying accurate options how does bacula figure out if a file needs to be backed up ? it's a simple AND ? As in if the options are Accurate = sm5 bacula will not backup the file if ((size = old size) AND (modtime = old modtime) AND (md5 = old md5)) Is that correct ? Do any of the options take precedence ? as in would be a file skipped if modif time is diffreent but it has the same md5sum ? Are there any implied options that you cannot ignore ? Practical case, ( bacula 5.0.1 ) I have to back-up a svn repo, in order to be able to make incremental backups as simple as posible i am hotcopying (client run before) it to another location, that bacula will backup ( then delete it with client run after). Now in the fileset i have Accurate = spnd5 This should tell bacula to take into consideration size , permission bits number of links , decreases in size and md5sum. However , an incremental is also including a full copy of the svn. What am i doing wrong ? it seems that it takes into account creation time even tho i have not specified it.

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• NIC reordering on RHEL5/CentOS 5

  - by ewwhite

  I have an HP ProLiant DL360 G6 containing two onboard NICs as well as an HP NC375T (NetXen NX3031 chipset) 4-port PCIe card. The system was running with eth0 and eth1 belonging to the onboard NICs and eth2-eth5 on the NetXen card. I recently rebuilt the server and from the kickstart process onward, the NICs were reordered such that the onboard NICs became eth4 and eth5, while the NetXen card took over eth0-eth3. I've had some experiences in the past where I tied NICs to specific interfaces via changes in the ifcfg-ethX config files, but this is the first time I've ever seen an add-in card take over eth0 from the motherboard's interfaces. This impacted my kickstart scripts, so: 1). How can I ensure that the onboard NICs take precedence in the kickstart arrangement. 2). What is the most consistent way to maintain that ordering through repeated reboots, kernel changes (e.g. going from a RHEL mainline kernel to a RHEL MRG realtime kernel), etc. 3). What is the interaction between the /etc/modprobe.conf module/NIC definitions, the /etc/sysconfig/network-scripts/ifcfg-ethX and the /etc/modprobe.d/blacklist functions in this context?

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• Configure Apache + Passenger to serve static files from different directory

  - by Rory Fitzpatrick

  I'm trying to setup Apache and Passenger to serve a Rails app. However, I also need it to serve static files from a directory other than /public and give precedence to these static files over anything in the Rails app. The Rails app is in /home/user/apps/testapp and the static files in /home/user/public_html. For various reasons the static files cannot simply be moved to the Rails public folder. Also note that the root http://domain.com/ should be served by the index.html file in the public_html folder. Here is the config I'm using: <VirtualHost *:80> ServerName domain.com DocumentRoot /home/user/apps/testapp/public RewriteEngine On RewriteCond /home/user/public_html/%{REQUEST_FILENAME} -f RewriteCond /home/user/public_html/%{REQUEST_FILENAME} -d RewriteRule ^/(.*)$ /home/user/public_html/$1 [L] </VirtualHost> This serves the Rails application fine but gives 404 for any static content from public_html. I have also tried a configuration that uses DocumentRoot /home/user/public_html but this doesn't serve the Rails app at all, presumably because Passenger doesn't know to process the request. Interestingly, if I change the conditions to !-f and !-d and the rewrite rule to redirecto to another domain, it works as expected (e.g. http://domain.com/doesnt_exist gets redirected to http://otherdomain.com/doesnt_exist) How can I configure Apache to serve static files like this, but allow all other requests to continue to Passenger?

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• Apache mod_proxy, how to forward request into local network ip(server)

  - by Beck

  Can't figure out, how to configure mod_proxy for this. I have two domains, one is working fine at the moment. Second is bind to the same ip. I need to forward requests from second domain to another server in local network. like that: domain1.com => 192.168.1.101 domain2.com => 192.168.1.102 What configuration or directives i should use? Thanks ;) Update <VirtualHost *:80> ServerName www.domain2.com ProxyRequests Off ProxyPreserveHost On <Proxy *> Order deny,allow Allow from all </Proxy> ProxyPass / http://192.168.1.103:8080/ ProxyPassReverse / http://192.168.1.103:8080/ </VirtualHost> It just doesn't redirect to second server. That's it. And when i restart apache, it says something with overlapping 80 port. [warn] _default_ VirtualHost overlap on port 80, the first has precedence

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• Coloring of collapsed threads in mutt

  - by Rich

  I'm trying to figure out the syntax of colouring collapsed threads in the mutt index. The documentation for mutt patterns doesn't seem to include a description of how this works, and so far I've been completely unable to figure it out by trial and error. What I'd like is for collapsed threads that contain any unread (new) messages to be always coloured green. If collapsed threads with no unread messages contain any flagged messages, then I'd like them to be red. So far, every set of patterns I've tried results in threads that contain both flagged and unread messages being coloured red (I want them green). These work: color index green default "~N" # unread messages color index green default "~N~F" # unread flagged messages color index red default "~F" # flagged messages color index green default "~v~(~N)" # collapsed thread with unread But these don't: color index green default "~v~(~N~F)" # attempt to keep threads with unread green color index red default "~v~(~F)" # colours collapsed threads with flagged and unread red color index red default "~v~(!~N~F)" # ditto color index red default "~v~(^!~N~F)" # ditto color index red default "~v~(~F)~(!~N)" # ditto color index red default "~v~(~F)~v~(!~N)" # ditto I've also tried switching the order of the "~v~(~F)" and "~v~(~N)" commands in the file, but the "flagged" rule always seems to take precedence over the "new" rule. Ideally I'd like to understand how the syntax for colouring collapsed threads works, but at this point I'd happily settle for a set of rules that achieves the colourscheme described above.

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• IPTables configuration help

  - by Sam

  I'm after some help with setting up IPTables. Mostly the configuration is working, but regardless of what I try I cannot allow localhost to access the local Apache only (i.e. localhost to access localhost:80 only). Here is my script: !/bin/bash Allow root to access external web and ftp iptables -t filter -A OUTPUT -p tcp --dport 21 --match owner --uid-owner 0 -j ACCEPT iptables -t filter -A OUTPUT -p tcp --dport 80 --match owner --uid-owner 0 -j ACCEPT Allow DNS queries iptables -A OUTPUT -p udp --dport 53 -j ACCEPT iptables -A OUTPUT -p tcp --dport 53 -j ACCEPT Allow in and outbound SSH to/from any server iptables -A INPUT -p tcp -s 0/0 --dport 22 -j ACCEPT iptables -A OUTPUT -p tcp -d 0/0 --sport 22 -j ACCEPT Accept ICMP requests iptables -A INPUT -p icmp -s 0/0 -j ACCEPT iptables -A OUTPUT -p icmp -d 0/0 -j ACCEPT Accept connections from any local machines but disallow localhost access to networked machines iptables -A INPUT -s 10.0.1.0/24 -j ACCEPT iptables -A OUTPUT -d 10.0.1.0/24 -j DROP Drop ALL other traffic iptables -A OUTPUT -p tcp -d 0/0 -j DROP iptables -A OUTPUT -p udp -d 0/0 -j DROP Now I have tried many permutations and I'm obviously missing everything. I place them above the in/out bound SSH to/from, so it's not the precedence order. If someone could give me the heads up on allowing only the local machine to access the local web server, that'd be great. Cheers guys.

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• CNAME vs A records

  - by deb

  I built a small rails app that allow users to make a simple site. It uses subdomain accounts ex: deb.myapp.com Whenever an user wanted to have a domain name associated with their site, they would change their NS records to point to slicehost where the application is hosted and I would manage the DNS records myself. However, as more people are using the application this is not an option for me anymore. I prefer users to keep their nameservers at goddady, register.com, etc, so they can log in and manage their own MX records or whatever else they need to change. My question is, should I have them change the A records to point to my server's ip, or should I have them create a CNAME record? Do they need to delete the default A records to allow the CNAME record to work? Will the A record take precedence and overrule the CNAME record? Thanks in advance. Sorry if this is a very basic question. I've read other posts and I can't find a definite answer.

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• JQuery Window blinking

  - by Nisanth

  Hi All I am developing a chat application(Customer and operator). Using jquery Ajax and PHP . From customer side he can handle multiple chat.. For example ha have two chat.. How he knows in which window the new msg comes.. I can take the count . But is there any option in jquery to blink the window when count change ?

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